Since the wankel rotary engine has invented, several rotary engines having paired rotors meshed with each other, such as the E. Martin's Multi-Stage Engine (U.S. Pat. No. 3,214,907 dated Nov. 2, 1965) and K. D. Sauder's Rotary Internal Combustion Engine (U.S. Pat. No. 3,724,427 dated Apr. 3, 1973), are invented up to the present. These engines all are inventions using the principle that the volume of a space made by recesses between projecting portions of rotors are changed as rotors rotate.
In internal combustion engines, the volume change in working chambers must progressively be made. In other words, one of a closed space in a working chamber must progressively be decreased or increased without opening to another space before finishing a unit process of compression or expansion. If the opening takes place, working fluid back flows, or irreversibly expands in a moment without producing power, which either results in loss of energe due to increase in entropy.
None of the said engines makes combustion gases fully expand to 1 atm only with one expansion chamber. Therefore, they must be comprised of plurality of segregated expansion chambers fully to expand combustion gases to 1 atm. This results in a complex and large-size construction. On the other hand, these engines having rotors meshed with each other cannot inherently resolve the problem of working fluid sealing because a clearance is required between the intermeshed rotors for absorbing the movement of thermal expansion of heated roters.
Thermodynamically, as well-known, the thermal efficiency of a constant-volume combustion engine is higher than that of a constant-pressure combustion engine operating under the same condition of compression ratio and cooling loss. For example, the thermal efficiency of the otto cycle on constant-volume combustion is higher than that of the diesel cycle on constant-pressure combustion operating at the same compression ratio. In otto cycle spark-ignition engines, however, the compression ratio of an engine is limited to some maximum value, to preclude preignition of a homogeneous air/fuel mixture. Therefore, the thermal efficiency is practically limited to some value. This problem is resolved somewhat by the compression-ignition diesel engine. Thus the compression ratio, and consequently the efficency, generally is higher than that of the spark-ignition engine. But because the system uses a heterogenous air/fuel mixture, the diesel engine operates at lower RPMs and therefore has a lower power output.
These problems can be overcome by the Ki W. Yang's Rotary Engine (U.S. Pat. No. 4,813,388, dated Mar. 21, 1989) which achives both constant-volume combustion and constant-pressure exhaust at a high compression ratio and a high RPM. The Yang's Engine, however, makes the new problem that its combustion chamber is not simple in construction and that a deadspace--though small, causing combustion gases irreversibly to expand somewhat without producing power--exists in its expansion chamber.
It is the ultimate object of the present invention to overcome the all problems stated above.